Preprint volume - SIBM

Pre-print Volume –Posters
Topic 4: THE ELASMOBRANCHS
between 1 and 3. Modelling studies indicate that optimal Lévy flight search patterns
occur with μ~2 (Viswanathan et al., 1999, 2000).
Results - While some final analyses are still being drawn together, it is clear from our
early results on basking shark, bigeye tuna, blue sharks, white tip sharks, leatherback
turtle and Magellanic penguin that Lévy behaviour is present. We found exponents for
individuals of these species with μ close to the optimum of 2. Although the analysis is
not yet complete some interesting differences have been identified between species. In
particular the billfish and the bigeye thresher shark have Lévy exponents close to 1.
These species perform diel vertical migrations (Sedberry and Loefer, 2001; Nakano et
al., 2003), resulting in long vertical displacements as they travel to and from deep
water which produce low Lévy exponents. It is an interesting confirmation of the
statistical methods that these known behavioural differences have been correctly
identified.
Conclusions – Using electronic tag data recording the diving movements of large
marine predators such as sharks and tunas, we show evidence for the presence and
diversity of Lévy behaviour. This provides the most comprehensive and convincing
support for the idea that organism search strategies evolved to exploit optimal Lévy
searches.
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41 st S.I.B.M. CONGRESS Rapallo (GE), 7-11 June 2010
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